Multi-function tube circuits for electrical signal processing



MULTI-FUNCTION TUBECIRCUITS FOR ELECTRICAL SIGNAL PROCESSING Filed March 14, 1962 3 Sheets-Sheet 2 4.5M@ 4 f Jaz//v IF v Jaa/w: ff v mvENToR. MA/Aw A. rfv/1M, .m BY @zg/ya @uw Aug. 25, 1964 D, R, TAYLQRD JR 3,146,303

MULTI-FUNCTION TUBE CIRCUITS FOR ELECTRICAL. SIGNAL PROCESSING Filed March 14, 1962 3 Sheets-Sheet 3 AGC' fici/ri my L:

United States Patent 3,146,303 MULTI-FUNCTION TUBE CIRCUITS FOR ELECTRICAL SEGNAL PROCESSING Donald R. Taylor, lr., Philadelphia, Pa., assigner to Philco Corporation, Phiia-deiphia, Pa., a corporation of Delaware Filed Mar. 14, 1962, Ser. No. 179,690 Claims. (Cl. 178-5.8)

This invention relates to circuits in which a single electron tube is caused to perform a plurality of functions. More particularly, this invention relates `to multifunction utilization of electron tubes of the general type in which electron ow from a single cathode is subject to control by a plurality of electrodes usually in the form of grids.

Such multigrid tubes, an example of which is the heptode or pentagrid tube, have been used for many years in radio and television. A well-known example of such use is the pentagrid converter commonly employed in broadcast receivers. However prior usages of the single cathode-multigrid type of tube have neither recognized nor utilized a characteristic of this type of tube which is the basis of the present invention.

The principal object of this invention is to effect economies in systems such as radio and television receivers. Primarily this invention reduces the tube complement in such a system and thereby effects reduction of cost, heating and power consumption.

This invention is based on the concept of utilizing the first grid of a tube of the above-mentioned type for performing a function which depends upon control of the intensity of the electron flow, and utilizing other electrodes for performing functions which do not depend upon intensity control but rather upon destination control of theelectrons.

It has been found that a tube of the above-mentioned type is uniquely characterized in that the first grid has substantially exclusive control of the intensity of the electron ow and the other grids are able only to control the destinations of the electrons. This unique characteristic enables utilization of such a tube according to this invention for the simultaneous performance of different functions. For example, as hereinafter described, the invention may be employed in a television receiver for simultaneous sound IF amplification and sync separation, or for simultaneous sound IF amplification and gated AGC (automatic gain control) action.

While the invention is applicable generally to systems in which it is necessary to perform simultaneously a plurality of different functions, since a television receiver is probably the most common environment for use of the invention it will be described with specific reference to such use.

Referring now to the accompanying drawings,

FIG. l is an explanatory illustration which will facilitate an understanding of the invention; and

FIGS. 2 to 5 are schematic illustrations of exemplary embodiments of the invention in a television receiver.

Referring first to FIG. 1, there is represented a heptode or pentagrid tube comprising a cathode, an anode, and ve successive grids therebetween which are numbered 1 to 5. For the purpose of illustration, it is assumed that grids 1, 3 and 5 are employed as control grids and have negative potentials applied thereto, and that grids 2 and 4 are employed as accelerating grids and therefore they together with the anode have positive potentials applied thereto. It will be understood of course that other modes of operation are possible. The electron flow is represented by the lines extending between the elements. The number of electrons leaving the cathode ice and constituting the total space current will be determined almost exclusively by the positive accelerating potential on grid 2 and the negative control potential on grid 1. Grid 1 thus possesses primary control of this total space current, but it cannot control the destinations of the electrons. That is, it has no control over the electron flow to the individual succeeding electrodes. Of the electrons arriving at grid 2, a certain portion leave the stream at that grid and the remainder proceed on to grid 4. This division of the electron stream at grid 2 depends on the negative control potential on grid 3 and the positive accelerating potential on grid 4. It is irnportant to note that grid 3 has no control over the cathode current but only determines how much is permitted to proceed onward to the succeeding electrodes and how much leaves at grid 2. Similarly, of the electrons arriving at grid 4, a certain portion leave the stream at that grid and the remainder proceed on to the anode, depending on the negative control potential on grid 5 and the positive potential on the anode.

Thusit will be seen that in any such tube where the electron ow is controlled by successive control grids, the total electron liow from the cathode is determined by the control applied between the first grid and the cathode, and the succeeding control grids serve only to determine the destinations of the electrons as between the plurality of electron-receiving electrodes. The present invention utilizes this unique characteristic of such an electron tube.

In practice the partition of space current and the degree of control of the various grids will be influenced by the physical structures of the grids, i.e. the neness of the winding pitch and the size of the wire used. This is advantageous, in practice of the present invention, since it provides flexibility of design for various applications of the invention.

I have found that because of the above-described characteristic of the single cathode-multigrid type of tube it is possible to utilize such a tube for the performance of different and independent functions. For example, the tube may be used in a television receiver of the intercarrier sound type both as a sound IF amplifier-limiter and as a sync separator. Generally speaking it is desirable to choose functions having Wide frequency separation. As hereinafter described it is possible to achieve performance of the different functions without appreciable modulating effect of one signal on another. However, if there is a wide frequency separation between the signals, any modulation that may be objectionable can easily be prevented or removed.

Referring now to FIG. 2, there is shown an embodiment of the invention in a television receiver in which a single tube is employed for performance of the abovementioned functions. Block 10 represents conventional television receiver circuits from which various signals may be derived. In this instance the 4.5 mc. sound IF signal is derived via connection 11 and the composite video signal, represented at 12, is derived via connection 13. These signals are supplied to a pentagrid tube 14 which serves the desired dual purpose.

In this instance the 4.5 mc. sound IF signal is supplied via tuned transformer 15 to the rst grid 16 of tube 14, and the amplified signal is derived from the fourth grid 17 via tuned transformer 1S. The operation is exactly equivalent to that of a normal pentode IF amplifier, with grid 17 in the role of pentode anode.

The composite video signal 12 is supplied with sync positive to the fifth grid 19 of tube 14 through the usual time constant arrangement for sync separation. Sync separation occurs in the normal self-levelling manner of a triode sync separator, the separation occurring at the .Si plate due to cut-off which is caused to occur early by reducing the plate supply voltage by means of a divider comprising resistors and 21. The usual capacitor 22 is provided to prevent video feedthrough.

Since the first grid 16. controls the total space current, the 4.5 mc. signal supplied thereto tends to modulate the sync signal derived from the anode. To prevent this a choke 23 is provided as shown. Moreover the capacitor 22 serves additionally to prevent such modulation from appearing in the separated sync output.

Since the grid 19 controls only a small fraction of the total space current and the anode circuit impedance at 4.5 mc. is high, there is insignificant modulation at grid 17 of the 4.5 current by the sync separating action.

Referring now to FIG. 3, in this instance the pentagrid tube 24 is made to serve the same functions as in FIG. 2 and is also made to serve additional functions. Again the 4.5 mc. sound IF signal, derived from circuits 25 via connection 26, is supplied to the first grid 27. In this instance, however, the 4.5 mc. outputs at grids 28 and 29 and the anode are added in the tuned` output 30 by means of trifilar coils. The operation is analogous to triode operation. Since the 4.5 mc. output is derived from grid 29 and the anode as well as grid 28, the division 0f the electron stream at grid 28 does not affect the 4.5 mc. output.

The composite video signal 31 with sync negative is derived from circuits 25 via connection 32 and is supplied to the third grid 33. This signal is amplified and inverted in polarity at grid 29 and is supplied to grid 34 through the usual time constant arrangement for sync separation which occurs in the usual manner by virtue of cut-off action. The separated sync is derived from the anode. Resistors 35 and 36 form a voltage divider to reduce the anode voltage and promote early cut-off. Capacitor 37 effectively removes any 4.5 mc. modulation of the sync output.

In addition to the aforementioned functions, noise protection is had by reason of the influence of the signal at grid 33 on grid 34 which prevents the latter from backing itself off. Furthermore sync separator type AGC voltage may be picked off at grid 34. Any noise pulse appearing at grid 33 will drive the latter into cut off and hence the noise pulse will not level at grid 34. Thus the tube serves additionally as a noise switch.

Referring now to FIG. 4, in this embodiment there is employed a split beam type tube 38 having a common cathode, two anodes and four grids. The 4.5 mc. sound IF signal is derived from circuits 39 via connection 4t) and is supplied to the first grid 41 of tube 38. The amplified 4.5 mc. signal is derived from the second grid 42 via the tuned output circuit 43, the operation being that of a triode amplifier.

The composite video signal 44 with sync negative is derived from circuits 39 via connection 45 and is supplied to grid 46. This signal, amplified and inverted in polarity, is derived from anode 47 and is supplied to grid 48 through the usual time constant arrangement for sync separation, the separated sync being derived at anode 49. Resistors 50 and 51 form a voltage divider to reduce the voltage at anode 49 and premote early cut-off. Capacitor 52 effectively removes any 4.5 mc. modulation of the sync output.

Since in this instance the grids 46 and 4S control only a small fraction of the total space current, there is insignificant modulation at grid 42. However, if desired the 4.5 mc. signal could be derived not only from grid 42 but also from anodes 47 and 49 by employing a trifilar arrangement such as that employed in the embodiment of FIG. 3.

As shown in FIG. 4, AGC voltage may be derived at grid 48. However, the noise protective feature obtained in FIG. 3 is not present.

Referring now to FIG. 5, there is shown another ernbodiment of the invention in which a pentagrid 53 is have no effect on the audio output.

made to serve both for sound IF amplification and for production of a gated AGC voltage. The 4.5 mc. sound IF signal is derived from circuits 54 via connection 55 and is supplied to the first grid through tuned transformer 56. The cathode and the first four grids constitute a pentode amplifier, the amplified 4.5 mc. signal being derived from grid 57 through transformer 58.

The composite video signal 59 with sync positive is derived from circuits 54 via connection 60 and is supplied to the fifth grid 61. Gated AGC action is effected in known manner by applying to the anode the fiyback pulses, one of which is shown at 62, which are produced in the horizontal defiection system. Resistors 63 and 64 are assigned proper values to apply the appropriate negative bias to grid 61 for the gated AGC action, i.e. so that the grid is driven only by the sync portions of signal 59. The voltage pulses produced at the anode are integrated by network 65 to produce the desired AGC voltage which is employed in the usual manner to control the gain of the receiver.

Referring now to FIG. 6, there is shown another embodiment of the invention in which a beam deflection type tube 66 is employed both for sound IF amplification and for audio amplification. The 4.5 mc. sound IF signal is supplied to the first grid through tuned transformer 67. The amplified sound IF signal is derived through bifilar transformer 68 as the sum of the plate currents.

The audio signal is applied push-pull to the beam deflection plates through transformer 69, and the amplified signal is derived through transformer 70 whose primary winding is connected so as to produce flux according to the difference in plate current. Thus, although capacitors 71 and 72 are provided to by-pass the IF, any IF currents in said primary will cancel one another and will And of course the audio has no effect upon the IF.

While several specific embodiments of the invention have been illustrated and described, it will be understood that the invention is not limited thereto but contemplates such modifications and further embodiments as may occur to those skilled in the art.

I claim:

1. In an electrical signal processing system wherein it is desired to perform two distinct functions in response to two different signals; an electron tube having a single cathode and a plurality of electron-receiving elements, first electrode means for controlling the intensity of the electron flow, and second electrode means for controlling the relative impingement of electrons on said receiving elements; means for supplying a first input signal to said first electrode means; means for deriving a first output signal resulting from the effect of said first input signal on said electron fiow; means for supplying a different and independent second signal to said second electrode means; and means for deriving a second output signal resulting from the effect of said second input signal on said electron fiow.

2. In an electrical signal processing system wherein it is desired to amplify a first signal having a relatively high frequency and it is also desired to derive from a second signal a relatively low frequency component; an electron tube having a single cathode and a plurality of electron-receiving elements, first electrode means for controlling the intensity of the electron stream from said cathode, and second electrode means for controlling the division of said stream between said receiving elements; means for supplying said first signal to said first electrode means; means for deriving said first signal in amplified form from at least one of said receiving elements; means for supplying said second signal to said second electrode means; and means for deriving said low frequency component of said second signal from another of said receiving elements.

3. In an electrical signal processing system wherein it is desired to perform two distinct functions in response to two different and independent signals; an electron tube having a single cathode, an anode, and a plurality of grids in succession between said cathode and said anode; means for supplying a first input signal to the first grid; means for deriving a first output signal from at least one of the other grids; means for supplying a different and independent second input signal to another of said grids; and means for deriving a second output signal from said anode.

4. In an electrical signal processing system wherein it is desired to perform two distinct functions in response to two different and independent signals; an electron tube having a single cathode, an anode, and a plurality of grids in succession between said cathode and said anode; means for supplying a first input signal to the first grid; means for deriving a first output signal from at least one of the other grids and said anode; means for supplying a different and independent second input signal to another of said grids; and means for deriving a second output signal from said anode.

5. In a television receiver wherein it is desired to amplify the sound IF signal and to separate sync from the composite video signal; an electron tube having a single cathode, at least one anode, and at least three grids in succession between said cathode and said anode; means for supplying the sound IF signal to a first of said grids; means for deriving the same signal in amplified form from a second of said grids; means for supplying the composite video signal with sync positive to a third of said grids; means including the latter grid and said anode for separating sync from the composite signal; and means for deriving the sync signal from said anode.

6. In a television receiver wherein it is desired to amplify the sound IF signal and to separate sync from the composite Video signal; an electron tube having a single cathode, an anode, and five grids in succession between the cathode and the anode, the second grid being connected to a source of positive potential and the third grid being connected to the cathode; means for supplying the sound IF signal to the first grid; means for deriving the same signal in amplified form from the fourth grid operating as the anode of a pentode; means for supplying the composite Video signal with sync positive to the fifth grid; means for causing the latter grid and the anode to separate sync from the composite signal; and means for deriving the sync signal from said anode.

7. `In a television receiver wherein it is desired to amplify the sound IF signal and it is also desired to amplify the composite video signal and to separate sync from the latter; an electron tube having a single cathode, an anode, and five grids in succession between said cathode and said anode; means for supplying the sound IF signal to the first grid; means for deriving the same signal in amplified form from the second and fourth grids and the anode; means for supplying the composite video signal with sync negative to the third grid, whereby the composite signal appears in inverted form at the fourth grid; means for supplying the inverted composite signal to the fifth grid; means for causing the latter grid and said anode to separate sync from the inverted composite signal; and means for deriving the sync signal from said anode.

8. A television receiver according to claim 7, further comprising means for deriving AGC voltage from the inverted composite signal.

9. In a television receiver wherein it is desired to amplify the sound IF signal and it is also desired to amplify the composite video signal and to separate sync from the latter; an electron tube having a single cathode, two anodes, first and second grids common to said anodes, and third and fourth grids individual respectively to said anodes; means for supplying the sound IF signal to the first grid; means for deriving the same signal in amplied form from the second grid; means for supplying the composite video signal with sync negative to the third '6 -grid,'whereby the composite signal appears'in inverted form at one of said anodes; means for supplying the inverted composite signal to the fourth grid; means for causing the latter grid and the other anode to separate sync from the inverted composite signal; and means for deriving the sync signal from said other anode.

10. A television receiver according to claim 9, further comprising means for deriving AGC Voltage from the inverted composite signal.

l1. In a television receiver wherein it is desired to amplify the sound IF signal and it is also desired to effect gated AGC action under control of the flyback pulses produced in the horizontal deection system; an electron tube having a single cathode, an anode and a plurality of grids in succession between said cathode and said anode; means for supplying the sound IF signal to the grid nearest the cathode; means for deriving the same signal in amplified form from a second of said grids; means for supplying the composite video signal with sync positive to a third of said grids; means for biasing the latter grid so that it is driven only by the sync portions of said composite signal; means for supplying said flyback pulses to said anode; and means for deriving AGC voltage from said anode.

12. In a television receiver wherein it is desired to amplify the sound IF signal and it is also desired to effect gated AGC action under control of the flyback pulses produced in the horizontal deflection system; an electron tube having a single cathode, an anode and five grids in succession between the cathode and the anode, the second grid being connected to a source of positive potential and the third grid being connected to the cathode; means for supplying the sound IF signal to the grid nearest the cathode; means for deriving the same signal in amplified form from the fourth grid operating as the anode of a pentode; means for supplying the composite video signal with sync positive to the fifth grid; means for biasing the latter grid so that it is driven only by the sync portions of said composite signal; means for supplying said flyback pulses to said anode; and means for deriving AGC voltage from said anode.

13. In a television receiver wherein it is desired to amplify both the sound IF signal and the audio signal; an electron tube having a single cathode, a control grid, two anodes, and a pair of beam-deflecting electrodes; means for supplying the sound IF signal to said control grid; means for deriving the same signal in amplified form as the sum of the anode currents; means for supplying the audio signal push-pull to said beam-defiecting electrodes; and means for deriving the audio signal in amplified form from said anodes.

14. In an electrical signal processing system; an electron tube having a single cathode; a plurality of electronreceiving elements, first electrode means for controlling the intensity of the electron flow, and second electrode means for controlling the relative impingement of electrons on said receiving elements; means including said first electrode means and one of said receiving elements for performing, in response to a first signal, a function which is dependent upon control of the intensity of the electron flow by said first electrode means; and means including said second electrode means and another of said receiving elements for performing, in response to a different and independent second signal, a second function which is dependent upon the control by said second electrode means of the relative impingement of electrons on said receiving elements.

15. In a television receiver wherein it is desired to amplify the sound IF signal and to perform another function in response to a received signal; an electron tube having a single cathode, at least two electron-receiving electrodes, and at least two electron-controlling electrodes; means for supplying the sound IF signal to the first of said controlling electrodes; means for deriving the sound IF signal in amplified form from at least one of 7 said receiving electrodes; means for supplying said received signal to the other of said controlling electrodes; and means for deriving from at least the other of said receiving electrodes a signal produced in response to said received signal.

UNITED STATES PATENTS Rust et al Oct. 27, 1936 

5. IN A TELEVISION RECEIVER WHEREIN IT IS DESIRED TO AMPLIFY THE SOUND IF SIGNAL AND TO SEPARATE SYNC FROM THE COMPOSITE VIDEO SIGNAL; AN ELECTRON TUBE HAVING A SINGLE CATHODE, AT LEAST ONE ANODE, AND AT LEAST THREE GRIDS IN SUCCESSION BETWEEN SAID CATHODE AND SAID ANODE; MEANS FOR SUPPLYING THE SOUND IF SIGNAL TO A FIRST OF SAID GRIDS; MEANS FOR DERIVING THE SAME SIGNAL IN AMPLIFIED FORM FROM A SECOND OF SAID GRIDS; MEANS FOR SUPPLYING THE COMPOSITE VIDEO SIGNAL WITH SYNC POSITIVE TO A THIRD OF SAID GRIDS; MEANS INCLUDING THE LATTER GRID AND SAID ANODE FOR SEPARATING SYNC FROM THE COMPOSITE SIGNAL; AND MEANS FOR DERIVING THE SYNC SIGNAL FROM SAID ANODE. 